Fused circuit breaker and method



Feb. 2, 1932. T. E. MURRAY, .JR 1,843,239

FUSED CIRCUIT BREAKER AND METHOD Filed Sept. 13, 1928 2 Sheets-Sheet 1 7 INVENTOR.

. l Muon/EY Feb. 2, 1932'. T. E. MURRAY, J'R

FUSED CIRCUIT BREAKER AND METHOD Filed Sept. l5, 1928 2 Sheets-Sheet 2 INVENTOR.

/IZQQ wli -lib BY Mt@ ATTORNEY Patented Feb. 2, 1932 *il-.UNITED STATES PATENT OFFICE THOMAS E. MURRAY, JR., OF BROOKLYN, NEW YORK, ASSIGNOR TO METROPOLITAN DE- 4 VICE CORPORATION, A CORPORATION 0F NEW YORK FUSED CIRCUIT BREAKER AND METHOD Application led September 13, 1928.

In a prior application Serial No. 257,861, iiled February 29, 1928, I have described a certain combination of circuit breakers and fuses adapted to simplify greatly the breaking ofhigh voltage circuits.

The present application provides certain improvements thereon.

The accompanying drawings illustrate embodiments of the invention.

Fig. 1 is a side elevation partly in section;

Fig. 2 is a perspective view showing a hand operated switch;

Fig. 8 is an elevation of a detail.

The incoming bus bar 1 of the circuit is mounted on an insulating barrier or other support 2 on the opposite side of which is a switch blade 3' pivotally carried by a support 4 connected to the bus 1.

According to Fig. 1, the switch blade is actuated through an arm 5 connected by an insulating link 6 to the core 7 of a quick-acting solenoid 8. According to Fig. 2, the switch blade is actuated by a handle 5a.

The outgoing bus 9 also mounted on the rear of the barrier carries a fixed blade 1() in line with an opening 11 registering with a lateral projection 12 on the switch blade. Under normal closed circuit conditions, the projection 12 engages the contact 1() and the full current flows from one to the other bus bar through the switch blade in the path indicated by the full line arrows. The switch blade has an extension 18 carrying a set of end contacts 14, 15 and 16 adapted to engage respectively certain blades 17, 18 and 19 which are separate from each other and separately mounted on identical brackets 20 which are carried by a common insulating support 21 mounted on the back of the barrier.

The contact blades 17, 18 and 19 are of successively increasing length so that as the switch is opened contact is maintained be tween all three blades (the position in Fig. 1) as the opening movement continues con tact is madeonly with blades 18 and 19 and finally contact is made only with blade 19; after which the further movement withdraws the switch contacts entirely from the blades.

Serial No. 305,677.

Each of the blades is supported on a shaft 22 in its bracket 2O and is free to rotate about the shaft. See Fig. 8. A light spring ,28 is fixed at one end to the shaft and has its opposite end bent under the edge of the blade. Consequently upon release of each blade it is swung up from the dotted position of Fig. 3 to the full line position. The

spring is not strong enough to pull the.

From each of the brackets 2O a branch containing a fuse passes to the outgoing bus 9, the current passing in the direction of the dotted line arrows.

A horizontal barrier 24 extends backward from the main barrier 2. The branches 25 and 26 of the fuse circuits are arranged on opposite sides of this barrier. Between each pair of leads 25 and 26 there is arranged a fuse, which may be of various types and are illustrated as of the type described in the foregoing Murray application.

The fuses 27, 28 and 29 corresponding respectively to the switch blades 17, 18 and 19 are of diiferent capacities as indicated by their relative diameter. The shortest blade controls the fuse of highest amperage and the longest blade the fuse of lowest amperage. For example, the blade 17 may control a 200 ampere fuse, the blade 18 a 100 ampere fuse andthe blade 19 a 10 ampere fuse. The number offuses and blades may be varied and the fuses may be of such different (or equal) capacities as to produce any desired change in the total fuse capacity as the switch moves from step to step. For example, in the above specific case, the fuse capacity at the instant the main switch is opened will be 31() amperes. Next it would drop to 110 amperes and finally to 10 amperes. The movement of the switch arm should be rapid so as to eect a wide separation between the main contacts before the breaking of the circuit by the blowing of the fuses, and thus to avoid the jumping of an arc across between the main contacts.

By the present arrangement of a fuse capacity which is varied, it is possible to secure a' wider separation of the ina-in contacts before blowing than where a single fuse or a fixed fuse capa-city is provided.

The principal improvement however is to ensure opening of high voltage circuits under all loads. For example, if the switch as shown in my pending application No. 257,861 is opened under load, and that particular load is of a smaller capacity than the fuse in circuit with it, this fuse, of course, will not blow and there will be no way to open the circuit. This present application takes care ofA any varying load. For example, if we use 200, 100 and 10 ampere fuses and we onen the switch while there is a 50 ampere load on the circuit, then the 20() ampere fuse will not blow nor will the 100 ampere fuse blow; but when the contacts have cleared the blades 17 and 18, the l0 ampere will blow. On the other hand, if we open the switch on 150 am pere load then the 100 and 10 ampere fuses will blow and the 20() ampere fuse will not blow. It should be kept in mind that the size of the fuses should vary depending on the size of the load that is to be broken. The smallest fuse should'be smaller than the smallest load.

Various modifications may be made by those skilled in the art without departing from the invention as defined in the following claims.

I claim:

l. An electric circuit including in combination a switch and a fuse device in shunt with the switch adapted to carry a current during the opening of the switch and to break the circuit thereafter, said fuse device being adapted to present a varying fuse capacity as the switch opens.

2. An electric circuit including in combination a switch and a fuse device in shunt with the switch adapted to carry' a current during the opening of the switch and to break the circuit thereafter, said fuse device having a capacity which diminishes during the opening of the switch.

3. An electric circuit including in colnbination a switch and a fuse device in shunt with the switch adapted to carry a Current during the opening of the switch and to break the circuit thereafter, said fuse device including a plurality of separate fuses and means for connecting them into the circuitin dif ferent combinations so to present different total Yfuse capacities.

1. An electric circuit including in combination a switch and a fuse device in shunt with the switch adapted to carry a current during the opening of the switch and to break the circuit thereafter, said fuse device including a plurality of separate fuses and separate contacts and said switch including a plurality of co-operating contacts and means for making such contacts in different combinations so as to provide different total fuse capacities in the circuit.

5. An electric circuit including in combination a switch, a fuse in shunt with the switch and (2o-operating contacts carried by the switch and the fuse, one of said contacts being automatically removable from operative position when the switch is opened.

6. An electric circuit including in combination a switch, a fuse and movable contact in line with the fuse and adapted to be engaged by a. aart of the switch when the latter is closed, and means for automatically rendering said contact inoperative when the switch is opened.

7. The method of breaking an electric circuit under load which consists in breaking a direct connection between the conductors while maintaining a fuse connection and gradually diminishing the fuse capacity to a point below the load so as to break the fused connection.

S. The method of breaking an electric circuit under load which consists in breaking a direct connection between the conductors while maintaining a fuse connection having a capacity less than the load and gradually diminishing such capacity as the break in the direct connection is widened.

In witness whereof, I have hereunto signed my name. Y

THOMAS E. MURRAY, JR. 

